Evidence-based FRC Targets for Centralised Chlorination in Emergencies

Problem

Current emergency water treatment guidelines stipulate what free residual chlorine (FRC) levels should be at water distribution points in refugee/IDP camps in order to protect water from microbiological contamination. The problem however is that the current guidelines are not based on any field evidence, instead deriving from conventions meant for municipal piped water systems. Field experience demonstrates that these guidelines fail to reliably protect water supplies in emergency settings.

We therefore set out to develop new guidelines for centralized chlorination in emergencies that are based on field evidence and are demonstrated to be effective for ensuring water safety at the point of consumption in the camp setting. We began the research in the Maban County camps in South Sudan, which we wrote about in the first blog post, then went to the Azraq refugee camp in Jordan over the course of two seasons, and then finally, to the Kigeme refugee camp in Rwanda.

This final blog post of our project brings together findings from our four field sites and presents new evidence-based chlorination targets that can help emergency WASH agencies ensure water safety in refugee/IDP camp settings.

Methods

We investigated how water quality changes between distribution at tapstands and consumption in shelters in refugee camp settings in South Sudan, Jordan, and Rwanda. We used the data to model post-distribution chlorine decay in order to determine how much free residual chlorine is required at distribution points in order to protect water for the entire duration of household storage and use. We evaluated household water safety effectiveness of current versus new chlorination guidelines by carrying out empirical checks against field data.

Findings

Overall, we found that current chlorination guidelines offer insufficient residual protection where ambient sanitary conditions are poor and/or temperatures are high (>30°C). In these settings, free residual chlorine levels at water distribution points must be increased in order to ensure adequate protection at point of consumption. Based on evidence from four refugee camp field sites, we have developed new evidence-based emergency chlorination targets that are designed for variable temperature and sanitary conditions (Table 1).

In Table 1: * ‘Ambient sanitary conditions’ reflect the overall environmental, domestic, and personal hygiene condition prevailing in the camp. It is assessed on the basis of whether Sphere standards for WASH indicators (water quantity, water access, sanitation coverage, etc.) are met or not. If multiple WASH standards are not met, it is classified as “poor”. If most or all WASH standards are met or exceeded, it is classified as “good”. For further details, please refer to the study report.

We evaluated how these new FRC targets performed with respect to ensuring household water safety compared to the current targets and found that the new targets ensured safe water at the household point of consumption 70-80% of the time, whereas the current targets only did so 15-50% of the time.

In addition to the new targets, our research also generated a number of other interesting findings:

• Microbiological water quality monitoring at the Kigeme refugee camp in Rwanda showed that E. coli indicator bacteria (and therefore pathogens) can exist at low levels of FRC (≤0.1 mg/L), indicating that FRC protection must be at least 0.2 mg/L when the last cup is consumed in the household to assure water safety (assumed as 24 hours after distribution from tapstands).
• Strong temperature dependence of chlorine decay means that seasonal changes in chlorination practice are required. For a ~10°C increase in ambient temperatures between seasons, delivery FRC should be increased by at least 0.5 mg/L over cool season lows to provide sufficient protection during hot seasons.
• In settings with poor ambient sanitary conditions and high temperatures (30 to 40°C, or higher) such as the Maban County camps in South Sudan, the desired level of household water safety (0.2 mg/L FRC at 24 hours post-distribution) could not be achieved by centralized chlorination. In these settings, we must either: (i) accept a shorter period of FRC protection (e.g., 10-12 hours) and supply water at more regular intervals to limit maximum household water age; and/or (ii) explore alternatives or adjuncts to centralized water treatment such as household water treatment.
• Findings from the Azraq refugee camp during winter/spring 2015 showed that the current FRC guideline (0.2-0.5 mg/L) can ensure household water safety, but only in settings that are very clean and cool.
• Observations at Azraq, Jordan show that beneficiaries may adopt a practice of storing treated water in direct sunlight in order to drive off chlorine when they perceive it to be excessive. Our findings demonstrate that direct sunlight exposure indeed promotes rapid chlorine decay. This highlights the need to better understand beneficiary preferences for water supply including chlorine taste/odour detection and rejection thresholds. Furthermore, the association between sunlight exposure and rapid chlorine decay suggests that opaque coloured containers may be better suited for preserving FRC. Further operational research is needed to investigate this relationship.

For further details, please see the full report.

Conclusions

In order to validate the new targets and use them to revise emergency chlorination guidelines, MSF undertook a validation study at a new field site at Mtendeli refugee camp in Tanzania in Fall 2016 (see the full report).

Overall, we found that the new FRC targets provided an adequate degree of household water safety at ~24 hours post-distribution (71% of samples passing the water safety threshold) and outperformed the current 0.2-0.5 mg/L guideline target (40% passing only). Now validated, these new evidence-based chlorination targets can be integrated into emergency water treatment guidelines. This process is under way for MSF and UNHCR field manuals, as well as for the current Sphere Guidelines revision process.

Next steps for emergency chlorination research include better understanding beneficiary taste/odour detection and rejection thresholds. These form an important upper limit to how much we should chlorinate camp water supplies.

Feature Photo: People collecting water at tapstand in the Batil refugee camp, South Sudan (April 2013). Credit: MSF.